6 Surgical oncology
Aetiology
The causes of malignancy are multifactorial. No single chemical or biological factor has been shown to cause cancer but a combination of factors, for example genetic susceptibility, chemicals, occupation, lifestyle and viruses, may induce malignant change in certain tissues in susceptible individuals (Table 6.1).
Table 6.1 Examples of causative factors in malignant disease
| Causative factor | Tumour | |
|---|---|---|
| Genetic | ||
Invasion and metastasis
The difference between a benign and a malignant tumour is the capacity to invade and metastasise. A benign tumour generally grows slowly, is always well encapsulated and may compress, but never invades, local tissues. In contrast, cancers invade surrounding tissues (Fig. 6.1) and spread to form distant tumour deposits (metastases).
Metastases occur by three routes (Fig. 6.2):
• lymphatic spread to local and distant nodes
• haematogenous spread (mainly to lung, liver and bone)
• transcoelomic (i.e. across a body cavity, e.g. peritoneum).
